Parenting styles are SO different

My ex lets our kids (7, 9, 12) stay up until like 10pm on her weeks and eat basically whatever. When they come to me on Friday, they're absolute nightmares for the first 24-48 hours - cranky, won't listen, act out. Once I get them back on a normal sleep schedule and routine, they're totally fine again. But then she gets mad when I "parent differently" and says I'm making them uncomfortable. I'm not trying to be a dictator, but they literally need sleep and vegetables. How do you not let this drive you insane?